Scientists at the Oak Ridge National Laboratory in the United States have used new technology to create a composite material that can increase the current capacity of copper wires. This provides a new material that can be used in ultra-efficient, high-power-density electric vehicle traction motors.
This research aims to reduce the obstacles encountered in the promotion of electric vehicles, including reducing the cost of ownership and improving the performance and life of components such as electric motors and power electronics. This material can be applied to any parts that use copper, including more efficient bus bars and smaller connectors for electric vehicle traction inverters, as well as wireless and wired charging systems.
In order to produce conductive materials with better performance and lighter weight, ORNL researchers deposited carbon nanotubes on a flat copper substrate to form a metal matrix composite material that has a better current than copper alone Processing capacity and mechanical properties.
Adding carbon nanotubes (CNTs) to the copper matrix to improve conductivity and mechanical properties is not a new idea. CNTs are a good choice due to their light weight, high strength, and good electrical conductivity. However, other researchers' attempts to produce composite materials in the past have very short lengths, only on the order of micrometers or millimeters, and the limited stretchability performance is also poor. If the material increases, the material performance becomes very poor.
The ORNL team decided to use electrospinning to deposit single-walled carbon nanotubes, which is a commercially viable method to create fibers when a liquid is sprayed through an electric field. The technology provides control over the structure and orientation of the deposited material, Li Kai explained, who is a post-doctoral researcher in ORNL's Department of Chemical Sciences. In this case, the process allows scientists to successfully orient the carbon nanotubes in a general direction to facilitate the flow of electric current.
Then, the research team used magnetron sputtering, a vacuum coating technology, to add a thin layer of copper film on the CNT-coated copper tape. The coated sample is then annealed in a vacuum furnace to form a dense and uniform copper layer, thereby creating a highly conductive copper-carbon nanotube network and allowing copper to diffuse into the carbon nanotube matrix.
Using this method, ORNL scientists created a copper-carbon nanotube composite material with a length of 10 cm and a width of 4 cm, with special properties. The microstructure characteristics of the material are analyzed by the instrument of the Nanomaterials Science Center of the US Department of Energy's Science User Facilities. The researchers found that compared with pure copper, the current capacity of this composite material increased by 14%, and the mechanical properties increased by 20%.
Tolga Aytug, the lead researcher of the project, said: "By embedding all the excellent properties of carbon nanotubes into the copper matrix, our goal is to improve mechanical strength, reduce weight and increase current capacity." Then you get a better Conductor and less power loss, which in turn improves efficiency and device performance. For example, improved performance means that we can reduce volume and increase power density in advanced motor systems. "
This work is based on ORNL's rich history of superconductivity research, which has produced excellent materials with low resistance and conductivity. The laboratory’s superconducting wire technology has been licensed to several industrial suppliers to enable high-capacity power transmission with minimal power loss.
Aytug said that while the new composite material breakthrough has a direct impact on electric motors, it can also improve electrification in applications where efficiency, quality and size are key indicators. He said that the improvement in performance characteristics achieved through commercially viable technologies means new possibilities for designing advanced conductors for a wide range of electrical systems and industrial applications.
The ORNL team is also exploring the use of double-walled carbon nanotubes and other deposition techniques, such as ultrasonic spray coating and roll-to-roll systems, to produce samples about 1 meter long.
Burak Ozpineci, ORNL's electric drive technology project manager and head of the Power Electronics and Motor Group, pointed out: "The motor is basically a combination of metal-steel sheet and copper winding." "In order to achieve the 2025 electric vehicle goal of the U.S. Department of Energy Office of Automotive Technology And the goal, we need to increase the power density of the electric drive and reduce the size of the motor by 8 times, which means improving the material performance."